[PATCH] mm: pagefault_{disable,enable}()

Introduce pagefault_{disable,enable}() and use these where previously we did
manual preempt increments/decrements to make the pagefault handler do the
atomic thing.

Currently they still rely on the increased preempt count, but do not rely on
the disabled preemption, this might go away in the future.

(NOTE: the extra barrier() in pagefault_disable might fix some holes on
       machines which have too many registers for their own good)

[heiko.carstens@de.ibm.com: s390 fix]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Nick Piggin <npiggin@suse.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 14 insertions, 14 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 93ef30ba209f..af7b81cbde30 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -282,9 +282,9 @@ static inline int get_futex_value_locked(u32 *dest, u32 __user *from)
 {
         int ret;
 
-        inc_preempt_count();
+        pagefault_disable();
         ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
-        dec_preempt_count();
+        pagefault_enable();
 
         return ret ? -EFAULT : 0;
 }
@@ -585,9 +585,9 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
         if (!(uval & FUTEX_OWNER_DIED)) {
                 newval = FUTEX_WAITERS | new_owner->pid;
 
-                inc_preempt_count();
+                pagefault_disable();
                 curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
-                dec_preempt_count();
+                pagefault_enable();
                 if (curval == -EFAULT)
                         return -EFAULT;
                 if (curval != uval)
@@ -618,9 +618,9 @@ static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
          * There is no waiter, so we unlock the futex. The owner died
          * bit has not to be preserved here. We are the owner:
          */
-        inc_preempt_count();
+        pagefault_disable();
         oldval = futex_atomic_cmpxchg_inatomic(uaddr, uval, 0);
-        dec_preempt_count();
+        pagefault_enable();
 
         if (oldval == -EFAULT)
                 return oldval;
@@ -1158,9 +1158,9 @@ static int futex_lock_pi(u32 __user *uaddr, int detect, unsigned long sec,
          */
         newval = current->pid;
 
-        inc_preempt_count();
+        pagefault_disable();
         curval = futex_atomic_cmpxchg_inatomic(uaddr, 0, newval);
-        dec_preempt_count();
+        pagefault_enable();
 
         if (unlikely(curval == -EFAULT))
                 goto uaddr_faulted;
@@ -1183,9 +1183,9 @@ static int futex_lock_pi(u32 __user *uaddr, int detect, unsigned long sec,
         uval = curval;
         newval = uval | FUTEX_WAITERS;
 
-        inc_preempt_count();
+        pagefault_disable();
         curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
-        dec_preempt_count();
+        pagefault_enable();
 
         if (unlikely(curval == -EFAULT))
                 goto uaddr_faulted;
@@ -1215,10 +1215,10 @@ static int futex_lock_pi(u32 __user *uaddr, int detect, unsigned long sec,
                         newval = current->pid |
                                 FUTEX_OWNER_DIED | FUTEX_WAITERS;
 
-                        inc_preempt_count();
+                        pagefault_disable();
                         curval = futex_atomic_cmpxchg_inatomic(uaddr,
                                                                uval, newval);
-                        dec_preempt_count();
+                        pagefault_enable();
 
                         if (unlikely(curval == -EFAULT))
                                 goto uaddr_faulted;
@@ -1390,9 +1390,9 @@ retry_locked:
          * anyone else up:
          */
         if (!(uval & FUTEX_OWNER_DIED)) {
-                inc_preempt_count();
+                pagefault_disable();
                 uval = futex_atomic_cmpxchg_inatomic(uaddr, current->pid, 0);
-                dec_preempt_count();
+                pagefault_enable();
         }
 
         if (unlikely(uval == -EFAULT))